Tubular core electric transformer

ABSTRACT

An electric transformer has a tubular iron core and its primary is located within the tube which can serve for secondary. In such case, the tubular iron core is short-circuited by a conductor connected to the tube extremities. The transformer may also have a secondary separate from the tubular iron core in which case the secondary has, preferably, likewise the form of a tube located within the tubular iron core and surrounding the primary. Both the primary and the secondary may consist of several turns. Such transformers are distinguished by exceptionally high values of power factor and efficiency, and are particularly suitable for heating, heat storing and energy shock absorbing purposes.

United States Patent 1191 [111 3,835,430 Kocsis Sept. 10, 1974 [54]TUBULAR CORE ELECTRIC 1,606,816 11/1926 Stevenson.... 336/83 2,107,1722/1938 Agricola 336/83 TRANSFORMER 3,305,811 2/ 1967 Toombs 336/83 [75]Inventor: Laszlo Kocsis, Budapest, Hungary 3,344,383 9/1967 Aberizk336/210 X Assignee: Transelectro Magyar villamossagi KulkereskedelmiVallalat, Budapest, Hungary Filed: Apr. 5, 1972 App]. No.: 241,473

Related US. Application Data Continuation of Ser. No. 37,467, May 18,1970, abandoned, which is a continuation of Ser. No. 774,986, Nov. 12,1968, abandoned.

Foreign Application Priority Data Sept. 20, 1968 l-lungary..- KO 2192US. Cl 336/83, 336/73, 336/174, 336/175, 336/212 Int. Cl. H011 17/06Field of Search 336/83, 212, 216,73, 174,

Primary ExaminerThomas J. Kozma Attorney, Agent, or Firm-Young andThompson [57] ABSTRACT An electric transformer has a tubular iron coreand its primary is located within the tube which can serve forsecondary. In such case, the tubular iron core is shortcircuited by aconductor connected to the tube extremities. The transformer may alsohave a secondary separate from the tubular iron core in which case thesecondary has, preferably, likewise the form of a tube located withinthe tubular iron core and surrounding the primary. Both the primary andthe secondary may consist of several turns. Such transformers aredistinguished by exceptionally high values of power factor andefficiency, and are particularly suitable for heating, heat storing andenergy shock absorbing purposes.

4 Claims, 12 Drawing Figures TUBULAR CORE ELECTRIC TRANSFORMER This is acontinuation of application Ser. No. 37,467, filed May 18, 1970, whichis a continuation of application Ser. No. 774,986 filed Nov. 12, 1968;both are now abandoned.

This invention relates to electric transformers.

As is known, in case of high secondary amperages the power factor ofconventional transformers is substantially less than unity. This is dueto considerable stray fields by which also the short-circuit current ofa transformer is'materially reduced.

The invention aims at eliminating such inconveniences by providing atransformer which is suitable for yielding high secondary amperages at apower factor of at least 0.9 and even more.

For this purpose, the invention suggests to employ a tubular iron corewith a primary therein. Viz., the basic idea of the invention is thatwith such tubular iron cores the flux path is the shortest and,therefore, the required exciting current the smallest. At the same time,due to its ferromagnetic nature, the tubular iron core may also servefor-secondary.

Further and closer details of the invention will be describedhereinafter by taking reference to the accompanying drawings which showvarious exemplified embodiments of the new transformer and in which:

FIG. 1 is a perspective view showing the principal features of theinvention.

FIG. 2 illustrates an equivalent electric circuit to FIG. 1.

FIG. 3 shows a perspective view of a practical embodiment of theinvention.

FIG. 4 is an exploded view of a detail of FIG. 3.

FIG. 5 represents a perspective view of another exemplified embodimentof the invention.

FIG. 6 illustrates an equivalent electric circuit to FIG. 5.

FIGS. 7 to-12 show similar views of further exemplified embodiments.

Similar details are referred to by same reference characters throughoutthe drawings.

As is shown in FIGS. 1 and 2, the transformer has a tubular iron coremade of ferromagnetic material such as iron. In the tubular iron core 20there is a primary 22 made of electrically conductive material such ascopper (Cu) and forming a primary circuit I between not specifiedterminals. The iron core 20 and the primary 22 are separated from oneanother by an insulation 24 such as mica. Moreover, the iron core 20being of ferromagnetic material may serve for secondary as well forwhich purpose it is short-circuited by a conductor 26 with which itforms a secondary circuit II.

In operation, the transformer works in the usual manner. A primary ac.voltage is applied to the terminals of the circuit I whereby a secondaryvoltage is excited in the secondary circuit II so that a secondarycurrent will flow through the iron core 20 and the conductor 26.

Such transformer is distinguished by a power factor of about 0.9 and isparticularly suitable for heating purposes, storing of heat, and takingup high shock loads if the insulation 24 is of refractory nature as inthe instant case.

A practical embodiment of the transformer according to the invention forheating purposes is illustrated in FIGS. 3 and 4. It is seen that thereare a pair of tubular iron cores 20a and 20b which are electricallyconnected with one another at their extremities to a closed electriccircuit by a pair of tubular yokes 28 and 30 made likewise offerromagnetic material such as iron. Both yokes 28 and 30 are, in acommon plane of the tubular iron cores 20a and 20b, subdivided into apair of crescent-shaped parts 28a, 28b and 30a, 30b, respectively. FIG.4 shows the subdivision of the tubular yoke 28. After the primary 22with its insulation 24 has been placed in the tubes 20a and 20b as wellas in suitable grooves of yoke parts 28a and 30a, the upper portions 28band 30b of the yokes are placed on top yoke parts 28a and 28b,respectively, and bonded with them by means of e.g. welding or brasing.The tubular yokes 28a, 28b and 30a, 30b are connected with the tubulariron cores 20a and 20b in a similar manner.

Obviously, the short-circuiting conductor 26 of FIGS. 1 and 2 is formedhere by the tubular yokes 28 and 30 which means that, on the one hand,there is practically no stray flux and, on the other hand, the secondarycurrent will flow in an iron body 20a, 20b, 28, 30 which not onlyprotects the primary 22 but also serves as a no-voltage heating means.

The exemplified embodiment illustrated in FIGS. 5 and 6 differs from theprevious one in that its secondary consists of a separate winding 28rather than of the tubular iron core 20 proper. It is made ofnon-magnetic but electrically conductive material such as brass so thatits resistance is lower than the resistance of the ferromagnetic tubulariron core 20. Moreover, it is likewise of tubular shape and is locatedwithin the tubular iron. core 20. Thereby, the secondary current willflow close to the primary 22 on a path well defined by the secondary 28.A transformer of such special arrangement may reach a power factor ofabout 0.99.

FIGS. 7 and 8 show an exemplified embodiment which is distinguished fromthe previous one by a tubular iron core composed of axially juxtaposedannular pieces such as rings punched out of core metal sheets as if itwere subdivided along planes transverse of the axial direction of thetransformer. Such subdivided annular pieces are referred to by referencecharacters 20/1, 20/2, 20/3. The significance of such embodimentconsists in that there are practically no Foucault currents (eddycurrents) which would flow in an integral tubular core 20. Thus, a hightransformer efficiency is obtained. Furthermore, the secondary circuitis, in the instant case, provided with terminals at which a load may beconnected since a transformer of such construction already permits totake off a secondary output and is distinguished by a maximum value ofthe power factor.

The exemplified embodiment illustrated in FIGS. 9 and 10 shows that thetransformer according to the invention may have several turns of primaryand/or secondary. In the instant case, there are one pair of primarywindings 22a and 22b, and one pair of secondary windings 28a and 28b,their corresponding insulations being designated by reference characters24a, 24b and 32a, 32b, respectively, and made e.g., of rubber.

FIGS. 11 and 12 represent an exemplified embodiment which differs fromthat according to FIGS. 7 and 8 in that some of the annular parts of thetubular iron core are made of a material of reduced electricalconductivity. In the instant case, annular parts 20/1, 20/2, 20/3 madeof a ferromagnetic material of greater conductivity such as ironpairwise sandwich annular parts 34/ l and 34/2, respectively, of lowerconductivity such as cast iron or, preferably, some antimagnetic steel.Moreover, all parts /1, 34/1, 20/2, 34/2, 20/3, etc., are mutuallyfixed, e.g., by means of applying an axial compressive force to themexceeding the yield points of the materials employed. Hereby, a rigidand very stable structure is obtained in which the iron core proper mayserve for supporting the other parts of the transformer.

It will be seen that the transformer according to the invention has thespecial feature of almost a complete lack of stray fluxes which is dueto the primary and, possibly, the secondary being disposed coaxiallyinside a tubular iron core which itself may serve also for secondary ifsuch use has special advantages as in case of 15 heating transformers.Measuring results obtained by conventional transformers and transformersaccording to the invention of same quality of iron cores and same valuesof induction as well as similar turn numbers are compared in thefollowing table:

where values characteristic of conventional transformers have been takenfor unity. It has to be pointed out that all values figuring in thetable can be obtained simultaneously. However, ifidependent on thenature of use, a certain magnitude has still to beimproved, it ispossible to size the transformer correspondingly at the expense of theremaining pair of values.

What we claim is:

1. In an electric heating transformer, a tubular solid iron core and atransformer primary within said tubular core and insulation within saidtubular core surrounding said transformer primary; the improvement inwhich said tubular core is in the form of a closed loop comprised by aplurality of iron core elements electri cally conductively bondedtogether by welding or brazing in electrically short-circuited relation.

2. A structure as claimed in claim 1, said tubular iron core comprisinga pair of tubular iron core elements disposed in a common plane andinterconnected at their ends by tubular iron yokes which are divided insaid plane into pairs of crescent-shaped parts.

3. A structure as claimed in claim 2, which is elongated in thedirection of said tubular iron core elements, said transformer primaryand insulation being continuous through one .of said yokes and emergingfrom said core through the other of said yokes.

4. A structure as claimed in claim 3, said yokes being semi-circular.

1. In an electric heating transformer, a tubular solid iron core and atransformer primary within said tubular core and insulation within saidtubular core surrounding said transformer primary; the improvement inwhich said tubular core is in the form of a closed loop comprised by aplurality of iron core elements electrically conductively bondedtogether by welding or brazing in electrically short-circuited relation.2. A structure as claimed in claim 1, said tubular iron core comprisinga pair of tubular iron core elements disposed in a common plane andinterconnected at their ends by tubular iron yokes which are divided insaid plane into pairs of crescent-shaped parts.
 3. A structure asclaimed in claim 2, which is elongated in the direction of said tubulariron core elements, said transformer primary and insulation beingcontinuous through one of said yokes and emerging from said core throughthe other of said yokes.
 4. A structure as claimed in claim 3, saidyokes being semi-circular.